The M813 Goanna (also know as the 'Anna' the 'Sturm' or 'The Bunker Buster')as a modified version of the Monitor, its main gun and layout rearranged to incorporate a 350mm Mortar. It started life as a refitted version of the Monitor that had suffered damage to the main gun. Its armament was originally thought to be a joke by HIGHCOM until it penetrated a bunker at 3000m. The vehicle has had its turret fixed and constructed as part of the supstructure, to provide more room and stability for the mortar.